The present invention relates to the video camera art. It finds particular application in conjunction with quality control and monitoring with video cameras and will be described with particular reference thereto. It is to be appreciated that the invention may find other applications including stop action photography, photographic archiving recording of slowly unfolding events, intermittent condition monitoring, video security, and the like.
Heretofore, charge coupled device (CCD) and other video cameras have generated a video output signal which included a long, continuous series of video image fields. In a transfer CCD camera, light was focused on an image section of a CCD sensor for a selected interval of time. The interval was selected to produce good image contrast with the amount of light received, e.g. 1/60th of a second. The charge on each element of the image section was indicative of received light intensity. The charge was transferred during a vertical blanking interval, e.g. a few hundred microseconds, into corresponding elements of an optically insensitive mass storage section. As the image section again commenced integrating received light, the charge was read out from the optically insensitive elements in the storage section element by element to form output values of a video signal representing one field of the resultant image. After the 1/60th of a second or other selected field interval, the charge representing the second field was transferred from the image section to the storage section. The image section started integrating light to form a third field and second field data was read from the storage section onto the video signal output. This sequence was repeated cyclically to form a video signal representing a series of single image fields.
This continuous production of image fields rendered CCD cameras awkward to adapt for certain high volume quality control situations. As objects were moved past the CCD camera, the resultant video signal represented a long series of image fields. In order to review the images of each object to monitor for a controlled characteristic, it was first necessary to determine which portion of the video signal included the field(s) which represented the monitored object. Second, it was necessary to determine within the field the actual location of the object. When increased lighting was necessary, the actuation of a strobe light was coordinated with the field of interest. If the strobe light was not completely coincident with a common location of the object within the field(s) of interest, lighting intensities and object shapes would vary among the fields of interest for each object. If the objects were moving rapidly compared with 1/60th of a second or other one field exposure time, then each object would be in a different position within the selected field of interest. This different positioning of the object not only required identifying the object position in the video field, but could also result in different lighting conditions on the object. These inaccuracies in the timing, positioning, and lighting of the monitored objects all limited the degree of accuracy and the speed with which quality control monitoring could be performed.
The present invention contemplates a new and improved video camera system which overcomes the above referenced problems and others.